Contact detection and laser power monitoring sensor for heat-assisted magnetic recording head

ABSTRACT

A slider configured for heat-assisted magnetic recording comprises a magnetic writer, a near-field transducer, and an optical waveguide coupling the near-field transducer to a light source. The writer is situated proximate the near-field transducer at an air bearing surface of the slider and comprises a first return pole, a second return pole, and a write pole situated between and spaced apart from the first return pole and the second return pole. A structural element is situated at or near the air bearing surface between the write pole and one of the first and second return poles. The structural element comprises a cavity. A thermal sensor is disposed in the cavity. The thermal sensor is configured for sensing contact between the slider and a magnetic recording medium, asperities of the medium, and output optical power of the light source.

RELATED PATENT DOCUMENTS

This application claims the benefit of Provisional Patent ApplicationSer. No. 62/385,016, filed on Sep. 8, 2016, to which priority is claimedpursuant to 35 U.S.C. § 119(e), and which is incorporated herein byreference in its entirety.

SUMMARY

Various embodiments are directed to an apparatus comprising a sliderconfigured for heat-assisted magnetic recording. The slider comprises amagnetic writer, a near-field transducer, and an optical waveguidecoupling the near-field transducer to a light source. The writer issituated proximate the near-field transducer at an air bearing surfaceof the slider and comprises a first return pole, a second return pole,and a write pole situated between and spaced apart from the first returnpole and the second return pole. A structural element is situated at ornear the air bearing surface between the write pole and one of the firstand second return poles. The structural element comprises a cavity. Athermal sensor is disposed in the cavity. The thermal sensor isconfigured for sensing contact between the slider and a magneticrecording medium, thermal asperities of the medium, and output opticalpower of the light source.

Other embodiments are directed to an apparatus comprising a sliderconfigured for heat-assisted magnetic recording. The slider comprises amagnetic writer, a near-field transducer, and an optical waveguidecoupling the near-field transducer to a light source. The writer issituated proximate the near-field transducer at an air bearing surfaceof the slider and comprises a first return pole, a second return pole,and a write pole situated between and spaced apart from the first andsecond return poles. A structural element is situated at or near the airbearing surface between the write pole and the first return pole. Thestructural element comprises a cavity. A thermal sensor is disposed inthe cavity. The thermal sensor is configured for sensing contact betweenthe slider and a magnetic recording medium, thermal asperities of themedium, and output optical power of the light source.

The above summary is not intended to describe each disclosed embodimentor every implementation of the present disclosure. The figures and thedetailed description below more particularly exemplify illustrativeembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Throughout the specification reference is made to the appended drawings,where like reference numerals designate like elements, and wherein:

FIG. 1 is a perspective view of a hard drive slider configured forheat-assisted magnetic recording (HAMR) in accordance with embodimentsdescribed herein;

FIG. 2 is a cross-sectional view showing details of a HAMR slideraccording to various implementations;

FIG. 3 illustrates a HAMR slider in accordance with some aspectsdescribed herein;

FIG. 4A shows a writer region of a HAMR slider which incorporates amulti-function sensor in accordance with various embodiments;

FIG. 4B shows various details of the slider region proximate themulti-function sensor shown in FIG. 4A;

FIG. 5A shows a writer region of a HAMR slider which incorporates amulti-function sensor in accordance with various embodiments;

FIG. 5B shows various details of a region proximate the multi-functionsensor shown in FIG. 5A;

FIG. 5C is a perspective view of the writer region shown in FIG. 5A;

FIG. 6A shows a writer region of a HAMR slider which incorporates amulti-function sensor in accordance with various embodiments;

FIG. 6B is a cross-sectional view of a portion of the writer regionshown in FIG. 6A;

FIG. 6C is a perspective view of the optical shield and NFT shown inFIGS. 6A and 6B;

FIG. 7A shows a writer region of a HAMR slider which incorporates amulti-function sensor in accordance with various embodiments;

FIG. 7B shows various details of a region proximate the multi-functionsensor shown in FIG. 7A;

FIG. 7C is a perspective view of a portion of the writer region shown inFIG. 7A;

FIG. 7D shows details of a thermal sensor shown in FIG. 7C;

FIG. 8A shows a writer region of a HAMR slider which incorporates amulti-function sensor in accordance with various embodiments;

FIG. 8B shows various details of a region proximate the multi-functionsensor shown in FIG. 8A;

FIG. 9A shows a writer region of a HAMR slider which incorporates amulti-function sensor in accordance with various embodiments; and

FIG. 9B shows various details of a region proximate the multi-functionsensor shown in FIG. 9A.

The figures are not necessarily to scale. Like numbers used in thefigures refer to like components. However, it will be understood thatthe use of a number to refer to a component in a given figure is notintended to limit the component in another figure labeled with the samenumber.

DETAILED DESCRIPTION

The present disclosure relates to heat-assisted magnetic recording,which can be used to increase areal data density of magnetic media. HAMRmay also be referred to as energy-assisted magnetic recording (EAMR),thermally-assisted magnetic recording (TAMR), and thermally-assistedrecording (TAR). In a HAMR device, information bits are recorded in astorage layer at elevated temperatures in a specially configuredmagnetic media. The use of heat can overcome superparamagnetic effectsthat might otherwise limit the areal data density of the media. As such,HAMR devices may include magnetic write heads for deliveringelectromagnetic energy to heat a small confined media area (spot size)at the same time the magnetic write head applies a magnetic field to themedia for recording.

A HAMR read/write element, sometimes referred to as a slider, recordinghead, read head, write head, read/write head, etc., includes magneticread and write transducers similar to those on current hard drives. Forexample, data may be read by a magnetoresistive sensor that detectsmagnetic fluctuations of a magnetic media as it moves underneath thesensor. Data is written to the magnetic media by a write coil that ismagnetically coupled to a write pole. The write pole changes magneticorientation in regions of the media as it moves underneath the writepole in response to an energizing current applied to the write coil. AHAMR slider also includes a source of energy, such as a laser diode, toheat the media while it is being written to by the write pole. Anoptical delivery path is integrated into the HAMR slider to deliver theenergy to the surface of the media.

The optical delivery path of a HAMR slider may include a plasmonictransducer proximate a media-facing surface (e.g., air-bearing surface,contact surface). The plasmonic transducer shapes and transmits theenergy to a small region on the medium. The plasmonic transducer issometimes referred to as a near-field transducer (NFT), optical antenna,surface plasmon resonator, etc., and may include a plasmonic metal suchas gold, silver, copper, aluminum, etc., and alloys thereof. Theplasmonic transducer for a HAMR device is very small (e.g., on the orderof 0.1 to a few light wavelengths, or any value therebetween) andcreates a localized region of high power density in the media through anelectromagnetic interaction. This results in a high temperature rise ina small region on the media, with the region reaching or exceeding theCurie temperature having dimensions less than 100 nm (e.g., ˜50 nm).

With reference to FIG. 1, a perspective view shows a HAMR sliderassembly 100 according to a representative embodiment. The sliderassembly 100 includes a laser diode 102 located on input surface 103 ofa slider body 101. In this example, the input surface 103 is a topsurface, which is located opposite to a media-facing surface 108 that ispositioned over a surface of a recording media (not shown) during deviceoperation. The media-facing surface 108 faces and is held proximate tothe moving media surface while reading and writing to the media. Themedia-facing surface 108 may be configured as an air-bearing surface(ABS) that maintains separation from the media surface via a thin layerof air.

The laser diode 102 delivers light to a region proximate a HAMRread/write head 106, which is located near the media-facing surface 108.The energy is used to heat the recording media as it passes by theread/write head 106. Optical coupling components are formed integrallywithin the slider body 101 (near a trailing edge surface 104 in thisexample) and function as an optical path that delivers energy from thelaser diode 102 to the recording media via a near-field transducer 112.The near-field transducer 112 is near the read/write head 106 and causesheating of the media during recording operations.

The laser diode 102 in this example may be configured as either anedge-emitting laser or surface-emitting laser. Generally, theedge-emitting laser emits light from near a corner edge of the laser anda surface emitting laser emits light in a direction perpendicular to asurface of the laser body, e.g., from a point near a center of thesurface. An edge-emitting laser may be mounted on the top surface 103 ofthe slider body 101 (e.g., in a pocket or cavity) such that the light isemitted in a direction parallel to (or at least non-perpendicular to)the media-facing surface. A surface-emitting or edge-emitting laser inany of these examples may be directly coupled to the slider body 101, orvia an intermediary component such as a submount (not shown). A submountcan be used to orient an edge-emitting laser so that its output isdirectly downwards (negative y-direction in the figure).

While the example in FIG. 1 shows a laser diode 102 directly mounted tothe slider body 101, the waveguide system 110 discussed herein may beapplicable to any type of light delivery configuration. For example, alaser may be mounted on the trailing edge surface 104 instead of the topsurface 103. In another configuration known as free-space lightdelivery, a laser may be mounted external to the slider 100, and coupledto the slider by way of optic fiber and/or waveguide. An input surfaceof the slider body 101 may include a grating or other coupling featureto receive light from the laser via the optic fiber and/or waveguide.

With reference now to FIG. 2, a cross-sectional view shows details of aHAMR apparatus 200 according to an example embodiment. Near-fieldtransducer 112 is located proximate a media-facing surface 202 (e.g.,ABS), which is held near a magnetic recording media 204 during deviceoperation. In the orientation of FIG. 2, the media-facing surface 202 isarranged parallel to the x-z plane. A waveguide core 206 may be disposedproximate the NFT 112, which is located at or near the media writingsurface 214.

The waveguide core 206 surrounded by cladding layers 208, 210. Thewaveguide core 206 and cladding layers 208, 210 may be made fromdielectric materials. Generally, the dielectric materials are selectedso that the refractive index of the waveguide core layer 206 is higherthan refractive indices of the cladding layers 208, 210. Thisarrangement of materials facilitates efficient propagation of lightthrough the waveguide. Light is delivered from the waveguide core 206along the negative y-direction where it is coupled to the NFT 112. TheNFT 112 delivers surface plasmon enhanced, near-field electromagneticenergy along the y-axis where it exits at the media writing surface 214.This may result in a highly localized hot spot (not shown) on the mediasurface 214 when the media 204 placed in close proximity to surface 202of the apparatus 200. Further illustrated in FIG. 2 is a write pole 212of the read/write head that is located alongside the NFT 112. The writepole 212 generates a magnetic field (e.g., perpendicular field) used inchanging the magnetic orientation of the hotspot during writing.

FIG. 3 shows a side view of a read/write transducer 302 configured forheat-assisted magnetic recording according to a representativeembodiment. The read/write transducer 302 may be used in a magnetic datastorage device, e.g., a hard disk drive. The read/write transducer 302may also be referred to herein as a slider, read/write head, recordinghead, etc. The read/write transducer 302 is coupled to an arm 304 by wayof a suspension 306 that allows some relative motion between theread/write transducer 302 and arm 304. The read/write transducer 302includes read/write transducers 308 at a trailing edge that are heldproximate to a surface 310 of a magnetic recording medium 311, e.g.,magnetic disk. The read/write transducer 302 further includes a laser320 and a waveguide 322. The waveguide 322 delivers light from the laser320 to components (e.g., a near-field transducer) near the read/writetransducers 308.

When the read/write transducer 302 is located over surface 310 ofrecording medium 311, a flying height 312 is maintained between theread/write transducer 302 and the surface 310 by a downward force of arm304. This downward force is counterbalanced by an air cushion thatexists between the surface 310 and an air bearing surface 303 (alsoreferred to herein as a “media-facing surface”) of the read/writetransducer 302 when the recording medium 311 is rotating. It isdesirable to maintain a predetermined slider flying height 312 over arange of disk rotational speeds during both reading and writingoperations to ensure consistent performance. Region 314 is a “closepoint” of the read/write transducer 302, which is generally understoodto be the closest spacing between the read/write transducers 308 and themagnetic recording medium 311, and generally defines the head-to-mediumspacing 313.

To account for both static and dynamic variations that may affect sliderflying height 312, the read/write transducer 302 may be configured suchthat a region 314 of the read/write transducer 302 can be configurablyadjusted during operation in order to finely adjust the head-to-mediumspacing 313. This is shown in FIG. 3 by a dotted line that represents achange in geometry of the region 314. In this example, the geometrychange may be induced, in whole or in part, by an increase or decreasein temperature of the region 314 via one or more heaters 316. A sensor315 is shown situated at or near the close point 314 of the writer ofthe read/write transducers 308. The sensor 315 is preferably a combinedcontact detection and laser power monitoring sensor in accordance withvarious embodiments.

Embodiments of the disclosure are directed to a HAMR slider whichincorporates a multi-function sensor configured for contact detectionand laser power monitoring. The multi-function sensor is situated at ornear the air bearing surface of the slider and can be used to monitorthe output optical power of a laser diode of the slider and detectcontact between the slider and a magnetic recording medium. In addition,the multi-function sensor can be used to monitor slider fly heightand/or detect thermal asperities of the medium. For example, during adetection mode, the multi-function sensor can be used to monitor sliderfly height and detect contact between the slider and a magneticrecording medium and/or thermal asperities of the medium. In a laserpower monitoring mode, the multi-function sensor can be used to monitorthe output optical power of the laser diode of the slider. Themulti-function sensor requires connection to only two electrical bondpads of the slider.

The region of a HAMR slider around the NFT and write pole can beconsidered a critical zone where the thermal gradient and magnetic fieldare generated for recording. Proper operation of components within thecritical zone requires very high fabrication accuracy. For example,designs for structures that are proximate the NFT tend to be verysensitive to process conditions. This sensitivity applies not only tostructure dimensions, location, and materials, but also to fabricationintangibles such as sputter re-deposition and milling-induced oxidedamage.

The NFT and write pole of a HAMR slider are subject to high temperatureduring operation, which can negatively impact the service life of thesecomponents. As such, it is desirable to provide monitoring of thesecomponents (e.g., sensing temperature, sensing output optical power ofthe laser diode). However, the optical and magnetic performance of theslider can be adversely impacted by the presence of structures (e.g., asensor) introduced into the critical zone. Moreover, the requirement ofvery high fabrication accuracy makes it challenging to fabricate suchstructures within the critical zone.

A region of the slider proximate the critical zone at or near the airbearing surface can be considered a parasitic zone. Optical and/ormagnetic elements can be installed within the parasitic zone whilenegligibly impacting the optical and magnetic performance of the slider.Structural elements can be formed within the parasitic zone with afabrication accuracy less stringent than those required for the criticalzone. Various embodiments of the disclosure are directed to a HAMRslider which incorporates a structural element and thermal sensor withinthe parasitic zone. Some embodiments are directed to a thermal sensorinstalled in a cavity within or formed by a structural element in theparasitic zone. It has been found that a thermal sensor installed in acavity within or formed by a structural element in the parasitic zoneprovides robust sensing performance, has negligible interaction withoptical or magnetic performance, does not increase the temperature ofthe critical zone, and has minimal interaction with critical optical ormagnetic fabrication.

FIG. 4A shows a writer region of a HAMR slider which incorporates amulti-function sensor in accordance with various embodiments. The writerregion shown in FIG. 4A includes a magnetic writer 402, an NFT 420, andan optical waveguide 422 which couples the NFT 420 to a light source(e.g., laser diode). The NFT 420, a terminal end of the opticalwaveguide 422, and components of the magnetic writer 402 are situated atan air bearing surface 450 (also referred to as a media-facing surface)of the slider.

The embodiment of the magnetic writer 402 shown in FIG. 4A includes afirst return pole (RP1) 404, a second return pole (RP2) 406, and a writepole 408 situated between and spaced apart from the first and secondreturn poles 404 and 406. A first coil (C1) 412 is situated between thewrite pole 408 and the first return pole 404. A second coil (C2) 410 issituated between the write pole 408 and the second return pole 406.Magnetic vias 414 can be included to magnetically couple variousmagnetic components of the magnetic writer 402. The NFT 420 is shown incontact with an angled portion of the write pole 408 proximate a writepole tip 409. As shown, the NFT 420 has an angled heat sink region incontact with the angled portion of the write pole 408 (e.g., an NTS ornear-field stadium design). A peg 421 of the NFT 420 is situatedadjacent the write pole tip 409. It is understood that the componentsand arrangement of components of the writer region can differ from thatshown in FIG. 4A in accordance with various designs.

The magnetic writer 402 further includes a structural element 430 shownsituated at the ABS 450. The structural element 430 is positionedbetween the write pole 408 and the first return pole 404. In theembodiment shown in FIG. 4A, the structural element 430 is a magneticstructure, such as a leading magnetic shield of the magnetic writer 402.According to other embodiments, the structural element 430 canconstitute a contact pad of the slider. A gap, g, is shown between theleading magnetic shield 430 and a terminal end portion of the firstreturn pole 404 proximate the ABS 450. The gap, g, can have a size ofbetween about 100 and 300 nm, for example. The gap, g, can be filledwith a dielectric material 432, such as alumina. The leading magneticshield 430 and gap fill material 432 define a structural element havinga cavity 435 at the ABS 450. A thermal sensor 434 is disposed in thecavity 435.

FIG. 4B shows an alternative configuration of the cavity 435 withinwhich the thermal sensor 434 is positioned. In the embodiment shown inFIG. 4B, the leading magnetic shield 430 extends to and connects withthe terminal end portion of the first return pole 404. The cavity 435 isformed within the leading magnetic shield 430 at the ABS 450, such thata portion of the leading magnetic shield 430 extends over the cavity 435and connects with the terminal end portion of the first return pole 404.The thermal sensor 434 is positioned within the cavity 435. A dielectricmaterial 432 can fill the remainder of the cavity 435 or cover thethermal sensor 434, which electrically insulates the thermal sensor 434from the leading magnetic shield 430 and first return pole 404.

The thermal sensor 434 is a multi-function sensor configured for sensingcontact and changes in spacing between the slider and a magneticrecording medium and for sensing output optical power of a light sourcecoupled to the NFT 420 via the waveguide 422. In some embodiments, thethermal sensor 434 is configured for sensing slider-medium contact,thermal asperities, and output optical power of the light source.According to various embodiments, the thermal sensor 434 comprises atemperature coefficient of resistance (TCR) sensor (e.g., a DETCR ordual-ended temperature coefficient of resistance sensor). For example,the thermal sensor 434 can be formed as a bar-shaped resistor. In otherembodiments, the thermal sensor 434 comprises a thermocouple. In furtherembodiments, the thermal sensor 434 comprises a photoresistive sensor.Notably, the multi-function thermal sensor 434 requires connection to amaximum of two electrical bond pads of the slider.

With the thermal sensor 434 positioned within the magnetic writer 402 asshown in FIGS. 4A and 4B, the thermal sensor 434 is warmed by theleading magnetic shield 430 due to light absorption (e.g., stray lightfrom the waveguide 408 and/or NFT 420) and thermal conduction. Changesin output optical power of the laser diode result in changes in lightabsorption by the leading magnetic shield 430, resulting incorresponding changes in the output of the thermal sensor 434. Theoutput of the thermal sensor 434 can be used to monitor the outputoptical power of the laser diode, such as during a laser powermonitoring mode. During a contact detection mode, the thermal sensor 434is responsive to temperature changes due to contact between the sliderand a magnetic recording medium and/or thermal asperities of the medium.The thermal sensor 434 is also responsive to temperature changesresulting from changes in slider fly height.

FIG. 5A shows a writer region of a HAMR slider which incorporates amulti-function sensor in accordance with other embodiments. The writerregion shown in FIG. 5A has a configuration similar to that shown inFIG. 4A. In particular, the writer region shown in FIG. 5A includes amagnetic writer 502, an NFT 520, and an optical waveguide 522 whichcouples the NFT 520 to a light source. The magnetic writer 502 includesa first return pole (RP1) 504, a second return pole (RP2) 506, and awrite pole 508 situated between and spaced apart from the first andsecond return poles 505 and 506. A first coil (C1) 512 is situatedbetween the write pole 508 and the first return pole 505. A second coil(C2) 510 is situated between the write pole 508 and the second returnpole 506. Magnetic vias 514 can be included to magnetically couplevarious magnetic components of the magnetic writer 502. The NFT 520 isshown in contact with an angled portion of the write pole 508 proximatea write pole tip 509. A peg 521 of the NFT 520 is situated adjacent thewrite pole tip 509.

The magnetic writer 502 further includes a structural element 530positioned adjacent the waveguide 522 and near the ABS 550. In theembodiment shown in FIG. 5A, the structural element 530 comprises ametallic optical element. For example, the metallic optical element 530may be configured as a bottom cladding disc (BCD) positioned adjacentthe core of the waveguide 522 in the bottom cladding. The metallicoptical element 530 comprises or is covered with a plasmonic metal oralloy, which serves to enhance the plasmonic excitation of the NFT 520.The metallic optical element 530 comprises a reflective surfaceconfigured to reflect stray light in a direction of the NFT 520. Thereflective surface of the metallic optical element 530 may also beconfigured to reduce back-reflection of light from the magneticrecording medium to the light source (e.g., to assist in laser mode hopreduction). The magnetic writer 502 also includes a leading magneticshield 536 situated between the metallic optical element 530 and thefirst return pole 504.

The metallic optical element 530 shown in FIG. 5A is spaced away fromthe ABS 550 such that a gap 535 is defined between the metallic opticalelement 530 and the ABS 550. The gap 535 can be filled with a dielectricmaterial, such as alumina. The metallic optical element 530 and gap fillmaterial 532 define a structural element having a cavity 535 at the ABS550. A thermal sensor 534 is disposed in the cavity 535. The dielectricmaterial 532 serves to electrically insulate the thermal sensor 534 fromthe metallic optical element 530 and the leading magnetic shield 536.With the thermal sensor 534 installed in the cavity 535 as shown in FIG.5A, the thermal sensor 534 is heated by the metallic optical element 530but does not negatively affect the optical function of the metallicoptical element 530 or the NFT 520.

FIG. 5B shows an alternative configuration of the cavity 535 withinwhich the thermal sensor 534 is positioned. In the embodiment shown inFIG. 5B, the metallic optical element 530 includes a notched regiondimensioned to receive at least a portion of the thermal sensor 534.Space in the cavity 535 between the metallic optical element 530 and thethermal sensor 534 can be filled with the dielectric material 532 or thethermal sensor 534 can be partially or completely covered by thedielectric material 532.

The thermal sensor 534 is a multi-function sensor of a type describedhereinabove. For example, the thermal sensor 534 can be configured forsensing slider-medium contact, thermal asperities, and output opticalpower of the light source, requiring connection to a maximum of twoelectrical bond pads. The thermal sensor 534 can comprise a TCR sensor(e.g., a bar-shaped resistor), a thermocouple or a photoresistivesensor.

FIG. 5C shows a different view of the embodiment illustrated in FIG. 5A.In FIG. 5C, the metallic optical element 530 is a bottom cladding discor BCD, which is shown spaced away from the ABS 550 and in contact witha first surface of the waveguide 522. The NFT 520 is positioned adjacentto a second surface of the waveguide 522 opposing the first surface andin contact with the write pole 508. The thermal sensor 534 is situatedat the ABS 550, residing within the space between the ABS 550 and theBCD 530. At this location, the thermal sensor 534 is heated by the BCD530 but does not adversely affect the optical function of the BCD 530 orthe NFT 520.

With the thermal sensor 534 positioned within the magnetic writer 502 asshown in FIGS. 5A and 5B, the thermal sensor 534 is warmed by themetallic optical element 530 due to light absorption (e.g., stray lightfrom the waveguide 508 and/or NFT 520) and thermal conduction. Changesin output optical power of the laser diode result in changes in lightabsorption by the metallic optical element 530, resulting incorresponding changes in the output of the thermal sensor 534. As isdiscussed above, the output of the thermal sensor 534 can be used tomonitor the output optical power of the laser diode (in a laser powermonitoring mode), monitor slider fly height, and detect contact betweenthe slider and a magnetic recording medium and/or thermal asperities ofthe medium (in a contact detection mode).

FIG. 6A shows a writer region of a HAMR slider which incorporates amulti-function sensor in accordance with other embodiments. FIG. 6B is across-sectional view of a portion of the writer region shown in FIG. 6A.The writer region shown in FIG. 6A has a configuration similar to thatshown in FIGS. 4A and 5A. In particular, the writer region shown in FIG.6A includes a magnetic writer 602, an NFT 620, and an optical waveguide622 which couples the NFT 620 to a light source. The magnetic writer 602includes a first return pole (RP1) 604, a second return pole (RP2) 606,and a write pole 608 situated between and spaced apart from the firstand second return poles 605 and 606. A first coil (C1) 612 is situatedbetween the write pole 608 and the first return pole 605. A second coil(C2) 610 is situated between the write pole 608 and the second returnpole 606. Magnetic vias 614 can be included to magnetically couplevarious magnetic components of the magnetic writer 602. The NFT 620 isshown in contact with an angled portion of the write pole 608 proximatea write pole tip 609. A peg 621 of the NFT 620 is situated adjacent thewrite pole tip 609.

The magnetic writer 602 further includes a structural element 630positioned at the ABS 650 adjacent the waveguide 622. In the embodimentshown in FIG. 6A, the structural element 630 comprises a metallicoptical element in the form of an optical shield. The optical shield 630serves as a reflector to reflect stray light in a direction of the NFT620. The optical shield 630 may also be configured to reduceback-reflection of light from the magnetic recording medium to the lightsource (e.g., to assist in laser mode hop reduction). The optical shield620 serves to generally improve the optical writing efficiency of theHAMR head (e.g., increasing NFT efficiency, improving the thermalgradient). In some embodiments, the optical shield 630 can extendthrough the waveguide 622 (e.g., through the waveguide core) and connectwith the NFT 620, as is indicated by the broken lines at the terminalend of the waveguide 622. A direct connection between the optical shield630 and the NFT 620 increases thermal conduction between the NFT 620 andthe thermal sensor 632.

A perspective view of the optical shield 630 relative to the NFT 620 isshown in FIG. 6C (noting that the waveguide has been removed in thisview). FIG. 6C provides a good view of the media-facing surface of theoptical shield 630, which includes the cavity 635 into which the thermalsensor 634 is installed and a flange region 631 proximate the peg 621 ofthe NFT 620. The magnetic writer 602 also includes a leading magneticshield 636 situated between the optical shield 630 and the first returnpole 604.

The optical shield 630 shown in FIGS. 6A, 6B, and 6C is formed toinclude a cavity 635. The cavity 635 is open to the ABS 650. A thermalsensor 634 is situated within the cavity 635. The space between thewalls of the cavity 635 and the thermal sensor 634 can be filled withthe dielectric material 632, such as alumina, or the thermal sensor 634can be covered with the dielectric material 632, which electricallyinsulates the thermal sensor 634 from the optical shield 630. It isnoted that in some embodiments, the dielectric material 632 may not beneeded given the small cross track width of the optical shield 630. Withthe thermal sensor 634 installed in the cavity 635 as shown in FIGS. 6A,6B, and 6C, the thermal sensor 634 is heated by the optical shield 630but does not negatively affect the optical function of the opticalshield 630 or the NFT 620.

The thermal sensor 634 is a multi-function sensor of a type describedhereinabove. For example, the thermal sensor 634 can be configured forsensing slider-medium contact, thermal asperities, and output opticalpower of the light source, requiring connection to a maximum of twoelectrical bond pads. The thermal sensor 634 can comprise a TCR sensor(e.g., a bar-shaped resistor), a thermocouple or a photoresistivesensor. In some embodiments, the thermal sensor 634 configured as a TCRsensor can have a cross-track width of about 1-5 μm and a down-trackthickness of about 50 nm. It is noted that, to increase the response ofthe thermal sensor 634, heatsinking of the optical shield 630 to thefirst return pole 604 can be reduced.

With the thermal sensor 634 positioned within the magnetic writer 602 asshown in FIG. 6A, the thermal sensor 634 is warmed by the optical shield630 due to light absorption (e.g., stray light from the waveguide 608and/or NFT 620) and thermal conduction. Changes in output optical powerof the laser diode result in changes in light absorption by the opticalshield 630, resulting in corresponding changes in the output of thethermal sensor 634. As is discussed above, the output of the thermalsensor 634 can be used to monitor the output optical power of the laserdiode (in a laser power monitoring mode), monitor slider fly height, anddetect contact between the slider and a magnetic recording medium and/orthermal asperities of the medium (in a contact detection mode).

FIG. 7A shows a writer region of a HAMR slider which incorporates amulti-function sensor in accordance with further embodiments. The writerregion shown in FIG. 7A has a configuration similar to that shown inFIGS. 4A, 5A, and 6A. FIG. 7C is a perspective view of a portion of awriter region of a HAMR slider that is similar to that illustrated inFIG. 7A, but includes a different write pole configuration. The writerregion shown in FIG. 7A includes a magnetic writer 702, an NFT 720, andan optical waveguide 722 which couples the NFT 720 to a light source.The magnetic writer 702 includes a first return pole (RP1) 704, a secondreturn pole (RP2) 706, and a write pole 708 situated between and spacedapart from the first and second return poles 705 and 706. A first coil(C1) 712 is situated between the write pole 708 and the first returnpole 705. A second coil (C2) 710 is situated between the write pole 708and the second return pole 706. Magnetic vias 714 can be included tomagnetically couple various magnetic components of the magnetic writer702. The NFT 720 is shown in contact with an angled portion of the writepole 708 proximate a write pole tip 709. A peg 721 of the NFT 720 issituated adjacent the write pole tip 709.

The magnetic writer 702 further includes a structural element 730 shownsituated at the ABS 750. The structural element 730 is positionedbetween the write pole 708 and the first return pole 704. In theembodiments shown in FIGS. 7A and 7C, the structural element 730 is amagnetic structure, such as a leading magnetic shield of the magneticwriter 702. The leading magnetic shield 730 is shown in contact with alayer of dielectric material, such as alumina, which together define astructural element having a cavity 735 into which a thermal sensor 734is installed.

FIG. 7B shows an alternative configuration of the cavity 735 withinwhich the thermal sensor 734 is positioned. In the embodiment shown inFIG. 7B, the leading magnetic shield 730 extends to and connects withthe terminal end portion of the first return pole 704. The cavity 735 isformed within the leading magnetic shield 730 at the ABS 750, such thata portion of the leading magnetic shield 730 extends under the cavity735 (along the ABS 730) and connects with the terminal end portion ofthe first return pole 704. The thermal sensor 734 is positioned withinthe cavity 735. A dielectric material 732 can fill the remainder of thecavity 735 or the thermal sensor 734 can be covered with the dielectricmaterial 732, which electrically insulates the thermal sensor 734 fromthe leading magnetic shield 730 and the first return pole 704.

The thermal sensor 734 is a multi-function sensor of a type describedhereinabove. For example, the thermal sensor 734 can be configured forsensing slider-medium contact, thermal asperities, and output opticalpower of the light source, requiring connection to a maximum of twoelectrical bond pads. The thermal sensor 734 can comprise a TCR sensor(e.g., a bar-shaped resistor), a thermocouple or a photoresistivesensor. As is shown in FIG. 7D, the thermal sensor 734, which may be abar-shaped resistor, can be wrapped in a dielectric material 732 toprevent electrical shorting.

With the thermal sensor 734 positioned within the magnetic writer 702 asshown in FIGS. 7A and 7B, the thermal sensor 734 is warmed by theleading magnetic shield 730 due to light absorption (e.g., stray lightfrom the waveguide 708 and/or NFT 720) and thermal conduction. Changesin output optical power of the laser diode result in changes in lightabsorption by the leading magnetic shield 730, resulting incorresponding changes in the output of the thermal sensor 734. As isdiscussed above, the output of the thermal sensor 734 can be used tomonitor the output optical power of the laser diode (in a laser powermonitoring mode), monitor slider fly height, and detect contact betweenthe slider and a magnetic recording medium and/or thermal asperities ofthe medium (in a contact detection mode).

FIG. 8A shows a writer region of a HAMR slider which incorporates amulti-function sensor in accordance with various embodiments. The writerregion shown in FIG. 8A is similar to that shown in previous figures,and includes a magnetic writer 802, an NFT 820, and an optical waveguide822 which couples the NFT 820 to a light source, such as a laser diode.The NFT 820, a terminal end of the optical waveguide 822, and componentsof the magnetic writer 802 are situated at an air bearing surface 850 ofthe slider.

The embodiment of the magnetic writer 802 shown in FIG. 8A includes afirst return pole (RP1) 804, a second return pole (RP2) 806, and a writepole 808 situated between and spaced apart from the first and secondreturn poles 804 and 806. A leading magnetic shield 805 extends alongthe ABS 880 between the write pole 808 and the first return pole 804. Asshown, the leading magnetic shield 805 is connected to the first returnpole 804. A first coil (C1) 812 is situated between the write pole 808and the first return pole 804. A second coil (C2) 810 is situatedbetween the write pole 808 and the second return pole 806. Magnetic vias814 can be included to magnetically couple various magnetic componentsof the magnetic writer 802. The NFT 820 is shown in contact with anangled portion of the write pole 808 proximate a write pole tip 809. Apeg 821 of the NFT 820 is situated adjacent the write pole tip 809.

The magnetic writer 802 further includes a structural element 830 shownsituated at the ABS 850. The structural element 830 is positionedbetween the write pole 808 and the second return pole 806. In theembodiment shown in FIG. 8A, the structural element 830 is a magneticstructure, such as a trailing magnetic shield of the magnetic writer802. According to other embodiments, the structural element 830 canconstitute a contact pad of the slider. A gap, g, is shown between thetrailing magnetic shield 830 and a terminal end portion of the secondreturn pole 806 proximate the ABS 850. The gap, g, can have a size ofbetween about 100 and 300 nm. The gap, g, can be filled with adielectric material 832, such as alumina. The trailing magnetic shield830 and gap fill material 832 define a structural element having acavity 835 at the ABS 850. A thermal sensor 834 is disposed in thecavity 835.

FIG. 8B shows an alternative configuration of the cavity 835 withinwhich the thermal sensor 834 is positioned. In the embodiment shown inFIG. 8B, the trailing magnetic shield 830 extends to and connects withthe terminal end portion of the second return pole 806. The cavity 835is formed within the trailing magnetic shield 830 at the ABS 850, suchthat a portion of the trailing magnetic shield 830 extends over thecavity 835 and connects with the terminal end portion of the secondreturn pole 806. The thermal sensor 834 is positioned within the cavity835. A dielectric material 832 can fill the remainder of the cavity 835or cover the thermal sensor 834, which electrically insulates thethermal sensor 834 from the trailing magnetic shield 830.

The thermal sensor 834 is a multi-function sensor of a type describedhereinabove. For example, the thermal sensor 834 can be configured forsensing slider-medium contact, thermal asperities, and output opticalpower of the light source, requiring connection to a maximum of twoelectrical bond pads. The thermal sensor 834 can comprise a TCR sensor(e.g., a bar-shaped resistor), a thermocouple or a photoresistivesensor.

With the thermal sensor 834 positioned at the trailing magnetic shield830 of the magnetic writer 802, light propagated along the waveguide 808and to the NFT 820 is largely blocked by the write pole 808. In theembodiment shown in FIG. 8A, a reflector 840 is provided to direct straylight to the trailing magnetic shield 830. The reflector 840 is shownsituated between the waveguide 822 and the leading magnetic shield 805.At least a portion of the reflector 840 is positioned out of plane withrespect to the write pole 808, allowing light to be communicated aroundthe write pole 808 and impinge on the trailing magnetic shield 830.Changes in output optical power of the laser diode result in changes inlight absorption by the trailing magnetic shield 830, resulting incorresponding changes in the output of the thermal sensor 834. As isdiscussed above, the output of the thermal sensor 834 can be used tomonitor the output optical power of the laser diode (in a laser powermonitoring mode), monitor slider fly height, and detect contact betweenthe slider and a magnetic recording medium and/or thermal asperities ofthe medium (in a contact detection mode).

FIG. 9A shows a writer region of a HAMR slider which incorporates amulti-function sensor in accordance with various embodiments. The writerregion shown in FIG. 9A has a configuration similar to that shown inprevious figures. In particular, the writer region shown in FIG. 9Aincludes a magnetic writer 902, an NFT 920, and an optical waveguide 922which couples the NFT 920 to a light source. The magnetic writer 902includes a first return pole (RP1) 904, a second return pole (RP2) 906,and a write pole 908 situated between and spaced apart from the firstand second return poles 905 and 906. A first coil (C1) 912 is situatedbetween the write pole 908 and the first return pole 905. A second coil(C2) 910 is situated between the write pole 908 and the second returnpole 906. Magnetic vias 914 can be included to magnetically couplevarious magnetic components of the magnetic writer 902. The NFT 920 isshown in contact with an angled portion of the write pole 908 proximatea write pole tip 909. A peg 921 of the NFT 920 is situated adjacent thewrite pole tip 909.

The magnetic writer 902 further includes a structural element 930 shownsituated at the ABS 950. The structural element 930 is positionedbetween the write pole 908 and the second return pole 906. In theembodiment shown in FIG. 9A, the structural element 930 is a magneticstructure, such as a trailing magnetic shield of the magnetic writer902. The trailing magnetic shield 930 is shown in contact with a layerof dielectric material, such as alumina, which together define astructural element having a cavity 935 into which a thermal sensor 934is installed.

FIG. 9B shows an alternative configuration of the cavity 935 withinwhich the thermal sensor 934 is positioned. In the embodiment shown inFIG. 9B, the trailing magnetic shield 930 extends to and connects withthe terminal end portion of the second return pole 906. The cavity 935is formed within the trailing magnetic shield 930 at the ABS 950, suchthat a portion of the trailing magnetic shield 930 extends under thecavity 935 (along the ABS 930) and connects with the terminal endportion of the second return pole 906. The thermal sensor 934 ispositioned within the cavity 935. A dielectric material 932 can fill theremainder of the cavity 935 or the thermal sensor 934 can be coveredwith the dielectric material 932, which electrically insulates thethermal sensor 934 from the trailing magnetic shield 930 and the secondreturn pole 906.

The thermal sensor 934 is a multi-function sensor of a type describedhereinabove. For example, the thermal sensor 934 can be configured forsensing slider-medium contact, thermal asperities, and output opticalpower of the light source, requiring connection to a maximum of twoelectrical bond pads. The thermal sensor 934 can comprise a TCR sensor(e.g., a bar-shaped resistor), a thermocouple or a photoresistivesensor. The thermal sensor 934 may be a bar-shaped resistor, which canbe wrapped in a dielectric material 932 to prevent electrical shorting.

With the thermal sensor 934 positioned at the trailing magnetic shield930 of the magnetic writer 902, light propagated along the waveguide 908and to the NFT 920 is largely blocked by the write pole 908. In theembodiment shown in FIG. 9A, a reflector 940 is provided to direct straylight to the trailing magnetic shield 930. The reflector 940 is shownsituated between the waveguide 922 and the leading magnetic shield 905.At least a portion of the reflector 940 is positioned out of plane withrespect to the write pole 908 to allow light to be communicated aroundthe write pole 908 and impinge on the trailing magnetic shield 930.Changes in output optical power of the laser diode result in changes inlight absorption by the trailing magnetic shield 930, resulting incorresponding changes in the output of the thermal sensor 934. As isdiscussed above, the output of the thermal sensor 934 can be used tomonitor the output optical power of the laser diode (in a laser powermonitoring mode), monitor slider fly height, and detect contact betweenthe slider and a magnetic recording medium and/or thermal asperities ofthe medium (in a contact detection mode).

Systems, devices or methods disclosed herein may include one or more ofthe features structures, methods, or combination thereof describedherein. For example, a device or method may be implemented to includeone or more of the features and/or processes above. It is intended thatsuch device or method need not include all of the features and/orprocesses described herein, but may be implemented to include selectedfeatures and/or processes that provide useful structures and/orfunctionality. Various modifications and additions can be made to thedisclosed embodiments discussed above. Accordingly, the scope of thepresent disclosure should not be limited by the particular embodimentsdescribed above, but should be defined only by the claims set forthbelow and equivalents thereof.

What is claimed is:
 1. An apparatus, comprising: a slider configured forheat-assisted magnetic recording and comprising a magnetic writer, anear-field transducer, and an optical waveguide coupling the near-fieldtransducer to a light source; the writer situated proximate thenear-field transducer at an air bearing surface of the slider andcomprising: a first return pole; a second return pole; and a write polesituated between and spaced apart from the first return pole and thesecond return pole; an optical or magnetic structural element at or nearthe air bearing surface between the write pole and one of the first andsecond return poles, the structural element comprising a cavity; and athermal sensor disposed in the cavity and separated from the structuralelement by a dielectric material so as to negligibly impact the opticalor magnetic performance of the slider, the thermal sensor configured forsensing contact between the slider and a magnetic recording medium,thermal asperities of the medium, and output optical power of the lightsource.
 2. The apparatus of claim 1, wherein the structural elementcomprises a magnetic shield.
 3. The apparatus of claim 2, wherein themagnetic shield comprises a leading magnetic shield of the writer. 4.The apparatus of claim 1, wherein the structural element comprises ametallic optical element.
 5. The apparatus of claim 4, wherein theoptical element comprises a reflective surface configured to reflectstray light in a direction of the near-field transducer.
 6. Theapparatus of claim 4, wherein the optical element comprises a reflectivesurface configured to reduce back-reflection of light from the medium tothe light source.
 7. The apparatus of claim 1, wherein the structuralelement comprises a contact pad.
 8. The apparatus of claim 1, whereinthe thermal sensor comprises a TCR (temperature coefficient ofresistance) sensor.
 9. The apparatus of claim 1, wherein the thermalsensor comprises a thermocouple.
 10. The apparatus of claim 1, whereinthe thermal sensor comprises a photoresistive sensor.
 11. The apparatusof claim 1, wherein the structural element is situated between the writepole and the second return pole.
 12. The apparatus of claim 1, whereinthe structural element comprises a trailing magnetic shield of thewriter.
 13. The apparatus of claim 1, wherein: the cavity comprises agap between the structural element and one of the first and secondreturn poles; and the thermal sensor is disposed in the gap.
 14. Anapparatus, comprising: a slider configured for heat-assisted magneticrecording and comprising a magnetic writer, a near-field transducer, andan optical waveguide coupling the near-field transducer to a lightsource; the writer situated proximate the near-field transducer at anair bearing surface of the slider and comprising: a first return pole; asecond return pole; a write pole situated between and spaced apart fromthe first and second return poles; an optical or magnetic structuralelement at or near the air bearing surface between the write pole andthe first return pole, the structural element comprising a cavity; and athermal sensor disposed in the cavity and separated from the structuralelement by a dielectric material so as to negligibly impact the opticalor magnetic performance of the slider, the thermal sensor configured forsensing contact between the slider and a magnetic recording medium,asperities of the medium, and output optical power of the light source.15. The apparatus of claim 14, wherein the structural element comprisesa leading magnetic shield.
 16. The apparatus of claim 14, wherein thestructural element comprises a metallic optical element.
 17. Theapparatus of claim 16, wherein the optical element comprises areflective surface configured to reflect stray light in a direction ofthe near-field transducer.
 18. The apparatus of claim 16, wherein theoptical element comprises a reflective surface configured to reduceback-reflection of light from the medium to the light source.
 19. Theapparatus of claim 14, wherein the structural element comprises acontact pad.
 20. The apparatus of claim 14, wherein the thermal sensorcomprises one of a TCR (temperature coefficient of resistance) sensor, athermocouple, and a photoresistive sensor.